1. Field of the Invention
The present invention relates to a fractionating apparatus comprising a probe for dripping a sample liquid fed from a liquid feed mechanism such as an HPLC (High Performance Liquid Chromatograph), with an additive agent solution, from a tip portion of the probe onto a plate such as a microplate or sample plate to move a sample, in which the fractionating apparatus prepares the sample to be analyzed by MALDI-TOF-MS (Matrix Assisted Laser Desorption Ionization Time-Of-Flight Mass Spectrometry).
2. Description of the Related Art
In the field of a proteohm analysis for elucidating the structure or action of protein or peptide, the MALDI-TOF-MS, which has lately gained attention, is employed for analysis. The MALDI-TOF-MS is a method for adding a matrix solution to a biosample and drying it to have a sample, then applying laser beam to the sample and ionizing it, and making the mass spectroscopy, in which the used amount of sample is as small as several μL.
A fat-soluble material is employed as the matrix compound, and a matrix solution is produced by dissolving the matrix compound in a solvent at high concentration. The matrix compound is excellently dissolved in an organic solvent of acetonitrile. However, in the case where the biosample is separated and eluted by the liquid chromatograph, the matrix solution is added simultaneously, and the sample solution is dripped for fractionation, the fractionation time is usually 10 minutes or more. Since the matrix solution of high concentration is always contact with the atmosphere at the tip portion of the probe, the solvent evaporates with the passage of time, so that the matrix compound deposits at the tip portion of the probe.
When the matrix compound deposits at the tip portion of the probe, the distance between the tip portion of the probe and the sample plate is not kept constant, and the dripping position is not determined, whereby it is difficult to produce the uniform liquid droplet.
Moreover, the measurement constituents separated and eluted from the HPLC are taken into the deposited matrix, making the analysis incorrect.
Therefore, in the related art, before dripping for fractionation, the tip portion of the probe is manually rinsed with a solvent of acetone, using a cylinder, to remove the matrix compound deposited at the tip portion of the probe.
The operation for manually washing the tip portion of the probe before fractionation operation is troublesome, and poor in workability.